Whisk together flour, brownie mix and brown sugar.
Using a spatula or wooden spoon, stir in eggs, butter and 5 tablespoons water. If the batter appears like there is too much flour add 1 more tablespoon of water. Batter will be very thick and somewhat sticky.
Fold in chocolate chunks
Preheat oven to 350 degrees. Grease a cookie sheet.
Use a jumbo cookie scoop (about 2 tablespoons) to drop rounds of dough on the cookie sheet about 2 inches apart. Bake for 8-10 minutes or until the edges are browned but the center has a bit of a shine.
Remove from oven, allow to cool 2 minutes on cookie sheet. Transfer to cooling rack to cool completely.
Notes
This batter is very thick and somewhat sticky. If it is too hard to work with initially you can chill it for a bit. I use a jumbo cookie scoop so that the cookies were uniform in size. If you don't have one use 2 tablespoons of rounded cookie dough. These cookies will spread a bit so make sure that they are at least 2 inches apart on the cookie sheet. Baking them for 8 minutes will give them a slightly underdone chewier texture. Cook for the full 10 minutes if you want them more cake like. Nutrition information for estimation purposes only.